1. Field of the Invention
The present invention relates to a method of producing a thin film magnetic head for high density recording.
2. Description of the Prior Art
It is known that a soft-magnetic thin film of a thin film magnetic recording head core for the use of high density recording in a hard disk drive has a magnetic flux path designated in a given direction for action of the magnetic head. The soft magnetic thin film is provided with uniaxial magnetic anisotropy so that a magnetic easy axis extends in a direction at a right angle to the magnetic flux path direction. Hence, a magnetic hard axis extends in the magnetic flux path direction, and thusly, a magnetic core with a higher permeability can be obtained. For fabricating such a magnetic head core and inducing uniaxial magnetic anisotropy in the core, an in-field electrodeposition method is provided in which a magnetic core thin film of a given pattern shape is selectively developed under a static magnetic field by electroplating of permalloy or FeCoNi alloy using the photoresist as a mask layer, or another method in which a thin film of Co amorphous alloy developed by sputtering is patterned to a magnetic core shape and heat treated under a fixed magnetic field. However, as the assembly pattern of the magnetic core is very small in size, its demage field effect decreases the effective field of the static external field in the electrodeposition process or the fixed magnetic field in heat treatment of the soft magnetic thin film of the magnetic core. Accordingly, the uniaxial magnetic anisotropy will hardly be induced in the magnetic core assembly using an external magnetic field.
More particularly, as its fine pattern produces a considerable degree of demagnetic field effect, the magnetic core thin film of a head will hardly be impressed with the strength of an external magnetic field, e.g. a static field in electroplating action or a fixed magnetic field in heat treatment. For overcoming such a drawback, a frame plating technique has been introduced, as disclosed in U.S. Pat. No. 3,853,715, in which the remaining portion of a substrate is also plated about and at an interval from the core assembly so that an external magnetic field can effectively be imposed during plating process.